Measurement of the quantity of particulates contained in a gas is demanded in some situations. For example, exhaust gas discharged from an internal combustion engine (for example, a diesel engine or a gasoline engine) may contain particulates such as soot.
Exhaust gas containing such particulates is purified by means of collecting the particulates through use of a filter. Therefore, if the filter suffers breakage or a like failure, unpurified exhaust gas is discharged directly to the downstream of the filter.
So, there has been demanded a particulate detection system which can detect the quantity of particulates contained in exhaust gas on the downstream side of the filter in order to directly measure the quantity of particulates contained in exhaust gas or to detect a failure of the filter.
For example, Patent Document 1 discloses a particulate measurement processing method and apparatus. Patent Document 1 discloses a method of jetting from a jetting hole an ionized gas which contains positive ions, mixing the ionized gas with a gas under measurement which is introduced into a channel and which contains particulates to thereby charge or electrify the particulates, and then releasing the charged particulates. The method detects a current (signal current) which flows in accordance with the quantity of the released, charged particulates, to thereby detect the particulate concentration.